Systems and methods for declarative specification, detection, and evaluation of happened-before relationships

ABSTRACT

A graphical user interface configured to facilitate replay debugging in distributed software programs is provided. The graphical user interface can allow the user to provide watchpoints and can allow the user to visualize variables that are contained within the log files. The watchpoints can represent one or more conditions. The user defined watchpoints can be converted into regex expressions and applied to the log files to determine if they meet the condition specified in the watchpoint, and if the log files meet the condition, a visual indication can be provided on a visual progress bar.

FIELD OF THE INVENTION

This disclosure relates to systems and methods for analyzing anddebugging distributed or multi-threaded events by replaying traces ofmessage communication execution logs. These systems and methods canemploy a visual progress bar that allows for a programmer and/orsoftware developer to review event logs to diagnose and debug programcode that is executed over a distributed or multi-threaded computingenvironment.

BACKGROUND OF THE INVENTION

In the field of computer science, distributed systems have been utilizedto allow for faster and more efficient execution of program code thatcan often prove overly cumbersome and computationally complex for asingle stand-alone system to effectively process. A distributed systemcan refer to a computing mode in which multiple networked computers“work together” by communicating and coordinating their actions toachieve a single result. Distributed systems can be bus based or eachindividual computing node can be networked to the other computing nodesin the distributed system. In a bus-based system, the components sendmessages to each other through the bus, by broadcasting the messages tothe bus such that every node of the system attached to the bus receivesthe message. In the context of computing, distributed systems consistingof multiple computers can work together to execute a single program,thereby spreading the computational burdens across the multiplecomputers so as to not overly burden any single computer.

The multiple computing resources organized in a distributed system cancommunicate and coordinate their actions by passing along messages toone another. In an example where multiple computers work together toexecute a single program, each computer can perform one or more tasksassociated with execution of the program, and they can pass messages toanother computer in the distributed system, wherein the message cancontain information required by the receiver to execute their taskwithin the program.

While distributed systems allow for faster computing speeds by breakinga program down into parts and spreading the computational burden acrossmultiple computers, the process of developing distributed softwareapplications can be difficult because if there is an error in the code,the source of the error may be difficult to ascertain since multiplemachines are each running different portions of the overall program, andaccess to the code that each machine is running individually may not bepossible or can be cumbersome to debug.

Debugging programs used to debug distributed software often attempt toidentify errors in the source code of the software run by eachdistributed component by employing a sequential debugger for software ineach component. Some distributed system software debuggers focus on thecommunications between components in the distributed system. Thesedebugging programs, known as replay debuggers, can focus on thecommunication events between components of the distributed system todetect unintended conditions among the messages or various faults, eachof which can provide clues as to the source of the program code error.

Replay debuggers can be characterized as belonging to one of twocategories: replay debuggers that replay the execution of thedistributed code in its entirety and replay debuggers, wherein only themessages communicated between components of the distributed system arereplayed.

In replay debuggers in which only the messages communicated betweencomponents of the distributed system are replayed, there has been along-felt need by programmers to have the ability to focus the replaydebugging on a subset of messages either manually or throughprogrammable constraints. Since the execution of a single distributedsoftware program can generate numerous messages between components,providing the developer the ability to focus only on a subset of themessages can be a valuable resource in debugging code.

The execution of a distributed software program may generate thousandsupon thousands of messages between components of a distributed system.Thus, if a programmer or developer was seeking to determine when aparticular condition in a message occurred, they would ordinarily berequired to sift through each and every message generated duringexecution of the replay debugger to see if the condition occurred. Thisprocess can prove to be extremely labor-intensive, further adding to thetime and complexity required to perform replay debugging.

SUMMARY OF THE INVENTION

Accordingly, systems and methods for constrained replay debugging withmessage communications are provided. In one example, a user interfacefor a replay debugger can employ a visual progress bar that allows aprogrammer or developer to visually see the progress of messages beinggenerated by the various components of a distributed system. By beingable to visually inspect the messages in an organized fashion that isfacilitated by the visual progress bar, a programmer or developer canmore efficiently diagnose and debug problems encountered with theexecution of their code.

In one or more examples, in conjunction with the visual progress bar,the replay debugger can be configured to allow for the developer tomanually constrain or highlight particular messages appearing in thevisual progress bar so that only a selected subset of the messagesappear or are highlighted. The replay debugger can provide adomain-specific Happened-Before-Language (HBL) to detect order dependentproperties among message logs through the specification of HBrelationships among the messages, components, and their variable valuesof components of the system. The language can permit the specificationof message types, components, and also logical expressions involvingmessage variables and component variables. Watchpoints may be definedusing HBL to detect specific conditions of the variables' values andmessage type occurrence. Detection of the watchpoints may be done on thelog of the messages or, in real time, or on the collected log file. Inone or more examples, and to facilitate detection, messages can beconverted to a log string in an intermediate standardized format overwhich watchpoints are specified using HBL. Regular expressions (regex)can be derived from the HBL-based watchpoint specifications and thenapplied to the log string. This approach can allow for the detection ofwatchpoints in real time or on messages collected in a log file. HBL canbe especially useful for detecting order dependent properties incyber-physical systems.

In one or more examples, the visual progress bar can be configured tosupport replay debugging during real-time execution with the ability tosave a subset of the message logs created based on criteria selected bythe user of the replay debugger. Additionally, and in one or moreexamples, the visual bar can be configured to provide a visual displayof watchpoint evaluation results, and additionally or in one or moreexamples, the visual progress bar can be configured to provide anautomate replay debug boundary setting based on user-programmableconstraints.

The systems and methods described above can be used by programmers orsoftware developers to visually inspect messages between componentsduring execution of distributed software for the purpose of debugging orother contexts in which viewing the messages generated betweencomponents in a distributed system can prove useful.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary distributed computing system configuredto execute a distributed software program according to examples of thedisclosure.

FIG. 2 illustrates an exemplary cyber-physical system that can utilize adistributed computing architecture according to examples of thedisclosure.

FIG. 3 illustrates an exemplary process for collecting and aggregatingmessages associated with the execution of a distributed software programaccording to examples of the disclosure.

FIG. 4 illustrates an exemplary graphical user interface for a replaydebugger according to examples of the disclosure.

FIG. 5 illustrates an exemplary operation of the variables visualizationportion of the replay debugger graphical user interface according toexamples of the disclosure.

FIG. 6 illustrates an exemplary replay debugger graphical user interfacewith watchpoint detection capability according to examples of thedisclosure.

FIG. 7 illustrates an exemplary system for generating a watchpointwithin a replay debugger graphical user interface according to examplesof the disclosure.

FIG. 8 illustrates an exemplary method for identifying patterns in aplurality of log files of a replay debugger according to examples of thedisclosure.

FIG. 9 illustrates an exemplary method for generating a visualization ofa watchpoint within a replay debugger according to examples of thedisclosure.

FIG. 10 illustrates an example of a computing device in accordance withone embodiment.

DETAILED DESCRIPTION OF THE INVENTION

In the following description of the disclosure and embodiments,reference is made to the accompanying drawings in which are shown, byway of illustration, specific embodiments that can be practiced. It isto be understood that other embodiments and examples can be practiced,and changes can be made, without departing from the scope of thedisclosure.

In addition, it is also to be understood that the singular forms “a,”“an,” and “the” used in the following description are intended toinclude the plural forms as well unless the context clearly indicatesotherwise. It is also to be understood that the term “and/or” as usedherein refers to and encompasses any and all possible combinations ofone or more of the associated listed items. It is further to beunderstood that the terms “includes,” “including,” “comprises,” and/or“comprising,” when used herein, specify the presence of stated features,integers, steps, operations, elements, components, and/or units but donot preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, units, and/or groupsthereof.

Some portions of the detailed description that follow are presented interms of algorithms and symbolic representations of operations on databits within a computer memory. These algorithmic descriptions andrepresentations are the means used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here, and generally,conceived to be a self-consistent sequence of steps (instructions)leading to a desired result. The steps are those requiring physicalmanipulations of physical quantities. Usually, though not necessarily,these quantities take the form of electrical, magnetic, or opticalsignals capable of being stored, transferred, combined, compared, andotherwise manipulated. It is convenient at times, principally forreasons of common usage, to refer to these signals as bits, values,elements, symbols, characters, terms, numbers, or the like. Furthermore,it is also convenient at times to refer to certain arrangements of stepsrequiring physical manipulations of physical quantities as modules orcode devices without loss of generality.

However, all of these and similar terms are to be associated with theappropriate physical quantities and are merely convenient labels appliedto these quantities. Unless specifically stated otherwise as apparentfrom the following discussion, it is appreciated that, throughout thedescription, discussions utilizing terms such as “processing,”“computing,” “calculating,” “determining,” “displaying,” or the likerefer to the action and processes of a computer system, or similarelectronic computing device, that manipulates and transforms datarepresented as physical (electronic) quantities within the computersystem memories or registers or other such information storage,transmission, or display devices.

Certain aspects of the present invention include process steps andinstructions described herein in the form of an algorithm. It should benoted that the process steps and instructions of the present inventioncould be embodied in software, firmware, or hardware, and, when embodiedin software, they could be downloaded to reside on and be operated fromdifferent platforms used by a variety of operating systems.

The present invention also relates to a device for performing theoperations herein. This device may be specially constructed for therequired purposes or it may comprise a general-purpose computerselectively activated or reconfigured by a computer program stored inthe computer. Such a computer program may be stored in a non-transitory,computer-readable storage medium such as, but not limited to, any typeof disk, including floppy disks, optical disks, CD-ROMs,magnetic-optical disks, read-only memories (ROMs), random accessmemories (RAMs), EPROMs, EEPROMs, magnetic or optical cards,application-specific integrated circuits (ASICs), or any type of mediasuitable for storing electronic instructions and each coupled to acomputer system bus. Furthermore, the computers referred to in thespecification may include a single processor or may be architecturesemploying multiple processor designs for increased computing capability.

The methods, devices, and systems described herein are not inherentlyrelated to any particular computer or other apparatus. Variousgeneral-purpose systems may also be used with programs in accordancewith the teachings herein, or it may prove convenient to construct amore specialized apparatus to perform the required method steps. Therequired structure for a variety of these systems will appear from thedescription below. In addition, the present invention is not describedwith reference to any particular programming language. It will beappreciated that a variety of programming languages may be used toimplement the teachings of the present invention as described herein.

Described herein are systems and methods for visualizing and replayingmessages generated between computing elements in a distributed computingsystem that is executing distributed software. In one example, thesystem can provide a user the ability to visualize the various messagesassociated with the execution of distributed software by providing avisual progress bar that supports the visualization of the chronologicalprogress of messages generated during execution of the distributedsoftware program. The visual progress bar can also be configured toallow for a user of the system to pause the replay, inspect individualmessages generated during the execution of the program, track thechanges of individual variables associated with the execution of theprogram, and step through the execution of the distributed programstep-by-step at the pace desired by a user of the system.

FIG. 1 illustrates an exemplary distributed computing system configuredto execute a distributed software program according to examples of thedisclosure. The example of FIG. 1 illustrates a distributed computingsystem 100 that includes a plurality of computing elements 102, 104,106, and 108. Each computing element 102, 104, 106, and 108 can includeboth a processor 102 a, 104 a, 106 a, and 108 a and a memory 102 b, 104b, 106 b, and 108 b respectively. The processor and memory of eachcomputing element can be utilized to execute a distributed softwareprogram in which portions of the overall program are executedindividually by each computing element. The computing elements cancoordinate their various actions by passing messages to one another thatindicate the status of variables or other information needed by acomponent to carry out its portion of the distributed program. Thesemessages can be referred to as “log streams” or “log files.” The presentdisclosure thus may use the term log stream and log fileinterchangeably. In one or more examples, each component of the system100 (i.e., 102, 104, 106, 108) can generate log streams 112 which canthen be stored in a memory (not pictured) thus creating a log file thatstores the contents of the log stream.

In one or more examples, each computing element 102, 104, 106, and 108can be communicatively coupled to one another via communication channels110 a-f. In one or more examples, communications through communicationschannel 110 a-f can be implemented using Wifi, Bluetooth, Ethernet, orany other type of communications channel known in the art to connect twoor more computing devices. In one or more examples, each computingelement can be connected to every other computing element that is partof the distributed system. Alternatively, each computing element may beconnected to only a subset of the computing elements that form thedistributed computing system.

Distributed computing systems can be utilized to coordinate theactivities of multiple computing elements to execute a common task. Forinstance a cyber-physical system can be implemented using a distributedcomputing environment. Cyber-physical systems can refer to systems thatinclude physical entities and mechanisms that are controlled andmonitored by computer-based processes. FIG. 2 illustrates an exemplarycyber-physical system that can utilize a distributed computingarchitecture according to examples of the disclosure. The system 200described with respect to FIG. 2 can be implemented in an elevatorsystem that transports people and/or objects from one floor of abuilding to another floor of a building. The system 200 can include aplurality of components 202, 204, 206, 208, 210, 212, and 214 that canbe used by the elevator system to facilitate the transport ofindividuals from one floor of a building to another.

Button controller 202 can represent the processor and memory associatedwith the buttons of the elevator that are manipulated by a user of theelevator to control which floor/floors the elevator goes to. Elevatorcontroller 204 can represent the processor and memory that can act asthe central computing element of the system 200 that can coordinate theactivities of each of the other elements attached to it. For instance,elevator controller 204 can be communicatively coupled to hydraulicscontroller 206 that coordinates the hydraulic components of the elevatorsystem, the car controller 208 that controls the elevator car, and doorprocessors 210, 212, 214, and 216, which control the individual doors ofeach floor of the building (in this example, the building has fourfloors).

Similar to the system described with respect to FIG. 1, the individualcomponents of the system 200 can coordinate their activities withrespect to executing a distributed software program by passing messagesto one another via communications channels 218 a-g. The distributedsoftware program being executed by the system 200 can be configured toallow each of the individual components of the system to work togetherto execute on the common goal of facilitation the operation of theelevator for ordinary use.

The system 200 can act as an example of a cyber-physical system thatutilizes a distributed computing architecture. When a software developeris developing distributed software such as the one used to operate thesystem 200, any errors in the code used to execute the system may bedifficult to diagnose and remedy because the code used to implement thesystem may reside on multiple components of the system. In the exampleof the system 200, if the elevator is not operating correctly due to abug in the software used to run the system, a developer may encounterdifficulty in locating where the bug is in the code because portions ofthe code reside on different devices.

In light of this difficulty, software developers have often turned toreplay debuggers to aid in the process of diagnosing and fixing errorsin the software that are encountered during the development process. Asthe name implies, replay debugging can involve the execution of asoftware program that is “recorded” and then played back in a controlledmanner to allow a software developer to step through the execution of asoftware program to pinpoint errors in execution. In the context of adistributed computing system that can execute a distributed softwareprogram, a replay debugger can utilize the messages that are generatedby components of the distributed system and passed between them to aidthe developer in diagnosing errors in distributed software. A replaydebugger can operate by collecting all of the messages generated duringthe operation of a distributed software program and presenting them tothe developer so that the developer can sort through them to determinethe root cause of an error.

However, the process of sorting through messages generated during theexecution of a distributed software program can be cumbersome since manysystems that employ a distributed computing environment can producecopious amounts of messages that are often not presented to the user inan organized manner that is meaningful to the developer. The process ofsifting through the messages passed between components in a distributedsystem can be cumbersome and inefficient. Oftentimes, the user of areplay debugger does not want to inspect each and every messageassociated with the execution of the distributed software but wouldrather see a subset of those messages, wherein the subset is defined bythe user's own constraints.

Furthermore, due to the large number of messages that can be generatedduring the execution of a distributed software program, simply providingmessages for a user to inspect during the debugging process may not bemeaningful if the user does not have a method to visualize thechronology and generation of the messages over time and ascertain howvarious values associated with the execution of the program change overtime.

A graphical user interface that can be configured to allow the user toconstrain the messages used for debugging and present the messages tothe user in a format and visual presentation that can facilitateefficient debugging can greatly reduce the amount of time required toengage in the replay debugging of a distributed software program. FIG. 3illustrates an exemplary process for collecting and aggregating messagesassociated with the execution of a distributed software programaccording to examples of the disclosure.

In order to configure a graphical user interface to operate with theabove described features, the data generated from the messages duringexecution of the distributed software program can be collected andorganized so as to facilitate the user of the replay debugger'sinteracting with the graphical user interface.

FIG. 3 illustrates an exemplary process for collecting and aggregatingmessages associated with the execution of a distributed software programaccording to examples of the disclosure. The process 300 can beconfigured to organize the messages generated during execution of adistributed software program into a plurality of logs that are organizedin a manner that facilitates operation of a graphical user interfacethat can make the replay debugging process more efficient.

The process 300 can begin at step 302, wherein execution of adistributed software program is started. As discussed above, adistributed software program can be executed over multiple computingelements. In one or more examples, at step 302, a portion of thedistributed software program can be executed according to a user'sspecification. Using the example of the elevator provided above, thedistributed software program associated with operation of the elevatorsystem and its components can be operated beginning with a specificoperation such as a user calling the elevator. In other words, step 302can represent the beginning of a simulation that tests the operation ofthe distributed software program used to run the elevator.

Once the execution of the software or simulation is started at step 302,the process 300 can move to step 304, wherein a log file is initiallycreated. As will be described further below, a log file can be ingestedby the graphical user interface of the replay debugger and used toprovide information to the user of the replay debugger about themessages generated during the operation of the software.

Once the initial log file is created at step 304, the process 300 canmove to step 306, wherein a timestamp and an index number can be writteninto the log file. Since the execution of a distributed software programcan be spread over multiple separate computing elements, there generallyis not a master clock or common clock between the components that can beutilized as a frame of reference to understand the time relationshipsbetween various messages passed between components of the distributedcomputing system. Thus, at step 306, once a log file has been generatedby the replay debugger, the generated log file can have a timestampwritten into the file by the replay debugger. In one example, the replaydebugger can establish time zero to be at step 302, wherein execution ofthe distributed software program under inspection is begun, and canstamp the log file generated at step 304 with the time that has elapsedsince the execution of step 302. For example, if 20 seconds has passedsince step 302 was executed and the log file was created at step 304,the replay debugger can write simulation time=20 seconds within thegenerated log file.

In addition to writing a time stamp at 306, the replay debugger can alsowrite an index number to the generated log file. The rate at whichmessages are generated during the execution of a distributed softwareprogram may exceed the resolution of the simulation time clock. Forinstance, if the simulation time is kept at a resolution of one second,but multiple log files are generated during that one second (i.e., forinstance, if log files are generated every millisecond), then the indexnumber can be used by the replay debugger to keep track of thechronological order of the log files within a given time frame. Forinstance, if 74 different log files are generated during the 20th secondof the software execution, then each of the log files can be writtenwith an index number one through seventy four indicating the order inwhich the logs were generated during the 20th second. In one moreexamples, the generated log file can have a timestamp written to it asdescribed above, have an index number written to it as described above,or both.

Once the timestamp and/or index number has been written to the generatedlog file at step 306, the process 300 can move to step 308, whereinmessages generated over a pre-determined time are recorded. As describedabove, during operation of a distributed software program, a pluralityof message can be generated by each of the components of the distributedcomputing system and transmitted to other components with thedistributed computing system. At step 308, the messages generated duringthe execution of the distributed computing system can be recorded, i.e.,stored in a memory. The messages can be recorded over a pre-determinedamount of time as set by a user or by the default specifications of thecode used to operate the replay debugger. In one or more examples, theuser of the replay debugger can manually constrain which messages theywish to be recorded. For instance, in a multi-component distributedcomputing system, the user of the replay debugger may desire to onlyreview the messages associated with a subset of the components in thedistributed computing system. Thus, in or more examples, the user of thereplay can be provided with a graphical user interface that can allowfor them to manually select which components of the distributed systemshould have their messages recorded during step 308.

Once the messages have been recorded at step 308, the process 300 canmove to step 310, wherein the messages are aggregated and written intothe log file. Aggregation can refer to the process of organizing thegenerated messages into a single log file or, in some examples, can alsorefer to the process of combining multiple log files into a single filethat can be ingested by the replay debugger.

Once the recorded messages have been aggregated and written into thegenerated log file at step 310, the process 300 can move to step 312,wherein the replay debugger can check to see if execution of thesimulation has been completed. Completion of the execution of thesimulation can either occur when a pre-determined amount of time hasexpired since the execution was started at step 302 or, in someexamples, can end when the end of the program itself is encounteredduring execution. If the execution of the simulation is determined tohave been completed, the process can move to step 314, wherein theprocess 300 is terminated. In one or more examples, terminating theprocess at 314 can include storing the generated log files in memory anduploading them to the computer or computing resources on which thereplay debugger resides. If execution is still on-going, the process 300can move back to step 304, wherein a new log file is generated and theprocess starts over.

Upon the completion of the process 300, the replay debugger can now haveone or more log files associated with the execution of the distributedsoftware program under inspection that provides information to the userregarding the messages generated during execution of the program. Theinformation can be organized to facilitate operation of the graphicaluser interface (described below). In one or more examples, after thecompletion of process 300, the multiple log files generated can beaggregated into a single log file that can be used by the graphical userinterface to provide a visual representation of the execution of thedistributed software program to the user.

FIG. 4 illustrates an exemplary graphical user interface for a replaydebugger according to examples of the disclosure. The graphical userinterface can be part of a replay debugging software suite that can bemade available to a software developer. The replay debugger can beaccessed via a cloud server in one or more examples, or it can be storedlocally on the machine of the software developer. In one or moreexamples, putting the replay debugger in a cloud server can facilitatemultiple people sharing their logs and files generated during theexecution of a particular portion of distributed software and canfacilitate collaboration between multiple developers. In the example ofa cloud-based system in which multiple users are able to access a commonreplay debugger, the replay debugger can be configured with a log-insystem to verify the credentials of an individual seeking access to thereplay debugger. The log-in system can also be used to identify whichuser has uploaded a log file to the system and can be used to identifywhich individual account each log file stored in the system belongs to.

As described above, the graphical user interface can be configured toprovide the user a way to visualize the progress of the execution of adistributed software program using log files generated by the processdescribed by the discussion with respect to FIG. 3. The log files can beeither manually uploaded to the replay debugging tool or in one or moreembodiments can be generated by the replay debugging tool when the toolis operating in a real-time mode (discussed further below).

The graphical user interface 400 can include a visual progress bar 402that can support visualizing progress of the replay debugging process bya user of the replay debugger. The visual progress bar 402 can representa timeline that can be manipulated by the user. The left side of theprogress bar 402 can represent the beginning (in time) of the log file,and the right side of the progress bar 402 can represent the end (intime) of the log file.

Graphical user interface 400 can also include a visual representation ofthe messages being generated at a specific time by the components withina distributed system as represented within the log file. The visualrepresentation 412 can illustrate the exact messages that are being sentat a particular moment in time correlated with the progress bar 402.Thus, if user clicks on the beginning of the visual progress bar 402,the log entries associated with the beginning of the visual progress bar402 visual representation 412 can illustrate the messages generated atthe beginning of the recording period. If the user clicks on the end ofvisual progress bar 402, the log entries associated with the end of therecording period can be illustrated at visual representation 412.

Visual representation 412 can illustrate the log entries by illustratingwhere the message originated (i.e., which computing element sent themessage), where the message was sent, and what can visually representthe contents of those messages. Using the example of the elevatorprovided in FIG. 2, and as illustrated in FIG. 4, at the instance oftime shown (i.e., simulation time=20 seconds), visual representation 412can illustrate that the elevator controller element received a messagefrom the 1st floor door component. Also as illustrated in FIG. 4, visualrepresentation 412 can include information about the contents of themessage. In the example illustrated, visual representation 412 showsthat the elevator controller received from the 1st floor door a messageindicating that the 3rd floor door was closed.

The progress bar 402 can include a play button 404. The play button 404can allow the user of the replay debugger to allow the recording to playand can also allow the replay debugger to pause the recording. When therecording (i.e., the log file) is allowed to play, visual representation412 can dynamically change to match the status of the message occurringat the precise time in the play back of the logs. Thus, as the log fileis being played back by the play button 404, the visual representationis changing based on the messages appearing in the log file at a giventime.

The visual progress bar 402 can also include a progress indicator 422.Progress indicator 422 can provide a visual representation to the userof the graphical user interface 400 of point in time of the execution ofthe distributed software that is currently being displayed on thescreen. In one or more examples, the further right along the visualprogress bar 402 that progress indicator 422 is located, the further intime the replay has progressed.

The visual progress bar 402 can also include a step forward button 408.The step forward button 408 can allow the user of the replay debuggingtool to “step through” the log file playback one log file at a time.Thus, when the step forward button 408 is pressed by the user (via amouse click in one example) the playback can advance to the next logfile in time. Upon pressing the step forward button 408, the visualrepresentation 412 can change to match the messages associated with thenext log file in time.

The visual progress bar 402 can also include, in one or more examples, astep back button 406. The step back button 406 can allow the user of thereplay debugging tool to “step back” through the log file playback onelog file at a time. Thus, when the step back button 406 is pressed bythe user (via a mouse click in one example), the playback can go back tothe previous log in time. Upon pressing the step back button 406, thevisual representation 412 can change to match the messages associatedwith the previous log file in time.

The graphical user interface 400 can include sliders 420 a and 420 b.Sliders 420 a and 420 b can be used by a user to limit the scope of thereplay, so that, rather than replaying the entire execution of thedistributed software program, the user can instead choose to only replaya portion of the execution. In one or more examples, a user of thegraphical user interface 400 can click on slider 420 a and 420 b andslide and place them along the visual progress bar 402. As an example,slider 420 a can be used by the user of the graphical user interface 400to indicate their preference of where the replay should begin. In oneexample, if the slider 420 a is placed at the very left end of thevisual progress bar 402, then the replay can begin at the very beginningof the execution of the distributed software program. However, if theslider 420 a is placed further to the right along the visual progressbar 402, the replay can begin at a time later than the beginning of theexecution. For example, the further right the slider 402 a is placedalong the visual progress bar 402, the later the replay of thedistributed software program can begin. In other words, the position ofslider 420 a can be proportional to the point in time at which thereplay of the distributed software program is to be started.

Slider 420 b can be used by the user of the graphical user interface 400to indicate their preference of where the replay should end. In oneexample, if the slider 420 b is placed at the very right end of thevisual progress bar 402, then the replay can end at the very end of theexecution of the distributed software program. However, if the slider420 b is placed further to the left along the visual progress bar 402,the replay can terminate at a time earlier than the end of the executionof the distributed software program. For example, the further left theslider 402 b is placed along the visual progress bar 402, the earlierthe replay of the distributed software program can terminate. In otherwords, the position of slider 420 b can be proportional to the point intime at which the replay of the distributed software program is to beterminated.

The graphical user interface 400 can also include a replay button 410.Replay button 410, when clicked by the user, can automatically begin thereplay of the distributed software program at the point in timeindicated by the position of slider 420 a (i.e., the beginning of thetime period). In the example where slider 420 a is to the far left endof the visual progress bar 402, if replay button 410 is clicked, thereplay can start over at the beginning of the execution of thedistributed software program. In the example where slider 420 a ispositioned at a point within the visual progress bar 402, when the userclicks on replay button 410, the replay can begin at the point in timeof the replay indicated by slider 420 a.

Also, as illustrated in FIG. 4, the graphical user interface 400 canalso include a variables section 414, a console section 416, and awatchpoints section interface 418. The variables section 414 (describedin further detail below) can indicate the status of various variablescontained with the messages that make up the individual log files. Theconsole section 416 can provide a space for a user to input variouscommands to the replay debugger tool. Watchpoint section interface 418can allow the user to visualize various watchpoints that have beeninserted into the playback of the log files (discussed in further detailbelow).

FIG. 5 illustrates an exemplary operation of the variables visualizationportion of the replay debugger graphical user interface according toexamples of the disclosure. The graphical user interface 500 of theexample of FIG. 5 can operate in substantially the same manner as theexample described with respect to FIG. 4. Therefore, for a detaileddiscussion of the components of the graphical user interface 500 (i.e.,elements 502, 504, 506, 508, 510, 512, 514, 516, and 518), thediscussion of their counterparts from FIG. 4 (i.e., elements 402, 404,406, 408, 410, 412, 414, 416, and interface) can be referenced.

The example of FIG. 5 illustrates the operation of the variables section514. The variables section 514 can illustrate the state of the variablesat each moment of time during the playback of the log file. In otherwords, variables section 514 can provide a summary of the status of thevarious variables being sent back and forth between the components ofthe distributed computing system. In the example of FIG. 5, variablessection 514 is illustrated as showing that, at the particular moment inthe playback, the elevator control is transmitting from the out port andhas received message “Reg 4.” The variables section 514 can list eachand every component visualized in visualization section 512 as well asthe variables passed in the messages between the components.

In one or more examples, one or more components listed in the variablessection 514 can be labeled with a dot 520. The dot 520 can indicate thatthe component experienced a change to one or more variables as a resultof a message passed to the component during the particular moment in thelog playback being visualized. This feature can be utilized as part ofthe debugging process. As an example, if the distributed softwareprogram under inspection exhibits a bug or crashes at a particularmoment during the playback of the log files, the variables section 514can be inspected to see which variables changed in that moment of time,and thus the variables section 514 can be used to help a softwaredeveloper ascertain the source of a failure of glitch.

In another example, the variables section 514 can be used to detect thepresence of malicious users or activity during the operation of thedistributed software program under inspection. As an example, if anunexplained change in the variable occurs as indicated by the variablessection 514, then the software developer can be alerted to thepossibility that the variable change was caused by an unauthorizedand/or malicious user who is manipulating the messages between theindividual components of the distributed computing system that isexecuting the distributed software program under inspection. In thisway, while the visualization section 512 allows a user to see theactivity occurring between components, the variables section 514 canallow the user of the replay debugger to visualize the substantivechanges to variables occurring during the visualized activity.

Returning to the example of FIG. 4, the graphical user interface 400 caninclude a watchpoints interface. A “watchpoint” can refer to aprogrammatic constraint, wherein the replay debugger analyzes the one ormore log files associated with a distributed software program todetermine if a pre-defined condition is true.

FIG. 6 illustrates an exemplary replay debugger graphical user interfacewith watchpoint detection capability according to examples of thedisclosure. The graphical user interface 600 of the example of FIG. 6can operate in substantially the same manner as the example describedwith respect to FIG. 4. Therefore, for a detailed discussion of thecomponents of the graphical user interface 600 (i.e., elements 602, 604,606, 608, 610, 612, 614, 616, and 618) the discussion of theircounterparts from FIG. 4 (i.e., elements 402, 404, 406, 408, 410, 412,414, 416, and interface) can be referenced.

In the example of FIG. 6, a user of the replay debugger can create andapply one or more watchpoints to the play back of the log filesassociated with execution of a distributed software program. Asdescribed above, a watchpoint can refer to a programmatic condition thatthe replay debugger can search for in a log file. A user can set up thewatchpoint, and the replay debugger can scan the log file or filesassociated with the distributed software program under inspection todetermine when the programmatic condition set by the user is true.

As an example, the user may want to know when a particular variableassociated with the log file is greater or less than a pre-definedvalue. In another example, the user may want to know when one variableassociated with the log file is greater or less than another variableassociated with the log file. In any of the above examples, the user canuser a graphical user interface (not pictured) to create their desiredwatchpoints.

Watchpoints interface 618 can provide a graphical user interface withinthe graphical user interface 600 to manage watchpoints created by theuser. As illustrated, each watchpoint created by the user can beidentified with a tag 626 that can identify the watchpoint's name (inthe example, the watchpoint is titled “Watchpoint 33”). In one or moreexamples, the tag 626 can include an icon 622 that, when manipulated bythe user (i.e., clicked on via mouse as an example), can delete thewatchpoint.

In this way, watchpoints interface 618 can provide the user of a replaydebugger a convenient and efficient means to manage all of thewatchpoints that have been programmed into the play back of thedistributed software program under inspection by the replay debugger.

In one or more examples of the disclosure, each tag 626 can include amenu 624 that is provides users with additional options with respect tothe watchpoint associated with the tag 626. In one example, and asdepicted in FIG. 6, the menu 624 can provide the user the option ofwhether they want to highlight when the watchpoint is true on the visualprogress bar 602 or provide a break to the replay when the watchpoint istrue.

When the highlight option of menu 624 is selected by the user, thereplay debugger can highlight the portions in time in which thewatchpoint condition is true on the visual progress bar 602. Asillustrated in the example of FIG. 6, the visual progress bar 602includes multiple highlighted portions 620. In one or more examples, thehighlighted portions 620 can represent time periods during the replay ofthe log file in which the condition corresponding to the watchpoint istrue.

When the break option of menu 624 is selected, the replay debugger canautomatically break (i.e., stop the replay of the log file) when thecondition set by the watchpoint is true. For instance, if a watchpointis set to trigger when a variable is above a pre-determined value, whenthe log file is played (by engaging play button 604), the replay willcontinuously play until the moment the watchpoint become true. At themoment when the watchpoint condition becomes true, the replay can“break,” meaning temporarily pause, until the user hits play again. Inthis way, the user can analyze the state of the log file at the precisemoment or moments when the pre-defined condition of watchpoint occurs.

In one or more examples, the replay debugger can also include areal-time playback capability. As described with respect to FIG. 2, inone or more examples, the distributed software program under inspectioncan be first executed and then have the generated log files aggregated,which can be then uploaded to the replay debugger. In one or moreexamples of the disclosure, the user can operate the graphical userinterface 400 in a real-time mode. When the graphical user interface 400is operated in real-time mode, once the user pushes the play button 404,the distributed software program under inspection is executed and thelog files generated are shown in real-time (i.e., as they are beinggenerated). If the user pauses the replay or goes back, then the replaydebugger can revert to its “replay mode,” in which the log filesdisplayed in the graphical user interface are shown after they have beengenerated.

The graphical user interface described above with respect to FIGS. 4, 5,and 6 can facilitate efficient replay debugging by providing the user aconvenient and intuitive way to visualize what the distributed softwareprogram under inspection is doing at any given time during itsoperation.

As discussed above, in order to debug a distributed software program, areplay debugger can use the message logs generated by the variouscomponents of a distributed computing system to diagnose issues thatexist within the distributed software program. Since oftentimes, in thecontext of a distributed software program, a user may not have access tothe entirety of the code (as it is often stored in the individualmemories of the components of the system), the user can use the messagespassed between the components to diagnose any issues. Thus, with respectto watchpoints, if the user wants to determine if and when any specifiedcondition occurs during the execution of a distributed software program,they may want to quickly and efficiently scan the generated message logsto search for specific conditions.

Thus, when a user is specifying a watchpoint, in essence, they areinstructing the system to parse through the various message logs tosearch for logs in which the condition specified by the user is true. Inorder to execute such a search, in one or more examples, the system caninitiate a pattern search through the plurality of message log filesgenerated during the execution of the distributed software program.

A simple example can illustrated the above concept. If a distributedsystem only generated four types of messages [m1, m2, m3, and m4] and auser wanted to identify all instances in which m1 came before m2 in anygiven log, then the user would need to review every single log file(which could be in the thousands or even tens of thousands) and searchfor instances in the log files in which m1 appears before m2. Such aprocess could be extremely labor intensive and tenuous and thereforelikely not feasible to implement.

As creating watchpoints can be characterized as an exercise inrecognizing specific patterns within text, the systems and methodsdescribed herein can utilize specific tools that have been developed fordiscovering patterns within large volumes of text, such as message logsgenerated during execution of distributed software program. Such tools,often referred to as string search algorithms or string matchingalgorithms, can quickly and efficiently analyze large volumes of textsto search for distinct patterns that can be specified by a user. Stringsearch algorithms can use a precise syntax to express the precisepattern to be searched within the body of text.

String search algorithms are generally configured to maximize theefficiency of a computing device to search through large volumes of textto search for distinct patterns within the text. A string searchalgorithm that does not take into account the processing capabilitiesand methodologies employed by computers can mean that the string searchalgorithm may not yield a computationally efficient process that canparse through a set of text quickly. In the context of the presentinvention, and specifically with respect to the replay debuggerdescribed above, not only must the string search algorithm be configuredto allow for quick processing of texts, but it should also beuser-friendly in that a user should be able to use a simple syntax toallow the user to quickly and easily set up a watchpoint.

Regular expressions are an example of a type of string search algorithmavailable to search for and identify specific patterns within a largebody of text. Regular expressions are a sequence of characters that candefine a specific pattern to search for in text. Regular expressions areoften times employed in web search engines, word processors, andprogramming languages to search for specific patterns. Specifically, aregular expression is a string of symbols (also referred to ascorrelation names or correlation variables) representing the pattern tobe matched. A regular expression can be built using one or more symbolsto represent characters in the search and one or more operators thatspecify the type of pattern to search for. Examples of operators includea concatenation operator (e.g., an “AND” operator between symbols in aregular expression may be used to indicate an AND relationship betweenthe symbols), alternation operator (e.g., a vertical bar ‘|’ mayseparate symbols in a regular expression indicating an OR condition forthe symbols), quantifiers, and grouping operators (e.g., indicated byparentheses). Examples of quantifiers include an asterisk ‘*’ that canindicate one or more occurrences of the symbol with which the quantifieris associated, a plus sign ‘+’ that can indicate occurrences of thesymbol with which the quantifier is associated, and a question mark ‘?’that can indicate zero or one occurrences of the symbol with which thequantifier is associated, reluctant quantifiers, as examples.

While regular expressions have proven to be a particularly useful way ofspecifying patterns to be search within text, it is not specified in auser-friendly manner. Regular expressions often employ convoluted andesoteric symbols and characters that are not easily understood andrequire a great deal of knowledge to employ. Thus, requiring that a usercreate a watchpoint by specifying a regular expression may make it morelikely that the user is unable to generate a watchpoint or will generatea watchpoint riddled with syntax errors, thereby making the watchpointunable to be implemented.

To illustrate the nature of regular expressions, an example is providedbelow. Assume that a definition file for a distributed software programincludes messages m1, m2, m3, and m4. If a user, using regularexpressions, desired to search a body of log messages to determineinstances in which m1 occurs before m2, the regular expression for sucha pattern may look like the following:(m1\[([{circumflex over ( )},\]]+),([{circumflex over( )},\]]+),([{circumflex over ( )},\]]+)\])((?>m1|m3|m4|)\[([{circumflexover ( )},\]]+),([{circumflex over ( )},\]]+),([{circumflex over( )},\]]+)\])*?(m2\[([{circumflex over ( )},\]]+),([{circumflex over( )},\]]+),([{circumflex over ( )},\]]+)\])

While the above regular expression is formatted and specified in amanner that can make the processing of such request faster and morecomputationally efficient, requiring a user to enter such an esotericand complex search declaration will likely lead to a poor userexperience and the inability to efficiently and effectively establishwatchpoints.

Thus, in order to allow a user to specify their search criteria in amore user-friendly and simplistic manner, an “intermediate” ordomain-specific language can be used that allows a user to specify asearch in a simplistic manner. The user's specification can then beconverted into a regular expression, which can then be executed by on aplurality of message logs to identify patterns that match the user'sspecification.

An example domain-specific/intermediate language is described below. Forpurposes of the discussion, the example provided below can be calledHappened-Before Language (HBL) and can represent a domain specificlanguage that can be employed by a user of a replay debugger to specifywatchpoints. The HBL language can be used to analyze log files. Toillustrate the functionality of the HBL language, assume a distributedsoftware program in which there are only four types of message types:m1, m2, m3, and m4. Also assume that each message type m1, m2, m3, andm4 can be sent to and from components with the example distributedsystem labeled c1, c2, c3, and c4. Thus, in an example, a log string andexpression such as m1[c1,c3] in the HBL language can represent messagetype m1 being sent from component c1 to component c3.

Given the specification of HBL described above, a log string in a replaydebugger can appear as follows:

m1[c1,c3] m1[c1,c2.c3] m1[c2,c1] m1[c3,*] m4[*,c3] m3[c1,c3] m1[c1,c2]m1[c1,c3] m1[c1,c3] m2[c2,c1] m1[c3,*] m4[*,c3] m2[c3,c2] m3[c1,c3]

The above string shows various message types (m1-m4) being sent byvarious components (c1-c4). The HBL can be configured to allow the userto search for various patterns within a set of logs. For instance, auser could enter the following command: m1→m2. The above command canspecify that the user is seeking to find all instances in which m1[*,*]happens before m2[*,*]. In other words, m2 must occur and m1 must occur,though in between, any message types other than m2 can occur. If theabove HBL specification is executed on the log string provided in theexample above, two results (i.e., hits) can occur as indicated below:

1. m1[c1,c3] m1[c1,c2.c3] m1[c2,c1] m1[c3,*] m4[*,c3] m3[c1,c3]m1[c1,c2] m1[c1,c3] m1[c1,c3] m2[c2,c1]

2. m1[c3,*] m4[*,c3] m2[c3,c2]

The above hits indicate patterns in the log string in which m1 appearsbefore m2. The user can not only search for patterns based on messagetype but can also search for message types sent to or from a specificcomponent within the distributed programming system. For instance, theuser can specify the following command using HBL: m1[c3,*]→m2. Thiscommand can indicate that the user wishes to search for all instances ina log string in which m1[c3,*] happens before m2[*,*]. In other words,rather than just searching for instances in which message type m1happens before m2, the search is more specific and is seeking instancesin which message type m1 is transmitted from c3 before message type m2occurs. Using the above log string, such a query can yield the followinghits:

1. m1[c3,*] m4[*,c3] m3[c1,c3] m1[c1,c2] m1[c1,c3] m1[c1,c3] m2[c2,c1]

2. m1[c3,*] m4[*,c3] m2[c3,c2]

In one or more examples, the user using HBL can specify specificchronological patterns of message types. In other words, rather thanjust specifying patterns in which m1 occurs before m2, a user canspecify to what degree m1 should come before m2. For example, if a userspecifies the following HBL command: m1→[2] m2, then the system cansearch for all instances in a specified log string in which m1[*,*]happens exactly two messages before m2[*,*]. In other words, m2 mustoccur, and any two message types can occur, and then m1 must occur.Using the log string example above, the following hit can be produced:

1. m1[c1,c2] m1[c1,c3] m1[c1,c3] m2[c2,c1]

In another example, the HBL language can also be configured to allow theuser to specify negative conditions. For instance, a user can set up awatchpoint by issuing the following command: m1→!m2. This command canindicate that the user wishes to search for all instances in a logstring in which m1[*,*] happens before m1, m3, or m4. Alternativelystated, m1, m3, or m4, but not m2, occurs after m1. A substring of thelog string that starts with m1 and ends with anything but m2 is a match.This substring will not include the ending message type of “anything butm2.” Note that there could be more than two message types in matches.Using the log string example from above, the above command can producethe following hits:

1. m1[c1,c3] m1[c1,c2.c3]

2. m1[c1,c2] m1[c1,c3]

3. m1[c3,*] m4[*,c3]

In one or more examples, the HBL language can employ variableexpressions. In one or more examples, variable expressions can beconstructed with variables using the following operators: NOT (!), AND(&&), OR (∥), ==, <, >. Therefore, a variable expression is an assertionthat can evaluate to a boolean value. In one or more examples, avariable expression can be used to identify events in which a variableis of a certain value or range of values. Variable expressions can beevaluated on every log file, or in one or more examples can be evaluatedin log files containing certain types of messages. For example, avariable expression that is combined with a → expression, can indicatedthat the variable expression is only to be evaluated on specificmessages corresponding to a matched substring, and may not be evaluatedon other logs. More specifically, when combined with a → relationship, avariable expression may be evaluated based on the semantics of as shownbelow.

-   -   m1→((c1.var1==5) && (m2.var3>32.2)) asserts that the variable        expression will evaluate to true at some time after m1 occurs.    -   m14 m2 ((c1.var1==5) && (var3 >32.2)) asserts that the variable        expression will evaluate to true at some time after m1 occurs.        Note that “var3” is unqualified, and therefore is is interpreted        as “m2.var3” using the “m2” outside of the parenthesis.    -   m1→[0] ((c1.var1==5) && (m2.var3 >32.2)) asserts that the        variable expression will evaluate to true immediately after m1        occurs.    -   m1→[5] ((c1.var1==5) && (m2.var3 >32.2)) asserts that in the        6^(th) log message prior to when the expression c1.var1==5) &&        (m2.var3 >32.2)) evaluates to true is of message type m1.    -   m1→[5] m2→[0] ((c1.var1==5) && (m2.var3 >32.2)) asserts that the        variable expression will evaluate true immediately after m2 that        occurs 5 message types after m1.

The above examples are provided only for purposes of illustration andshould not be construed as limiting. Furthermore, the above examplesillustrate only a portion of the HBL's capabilities, and the HBL can beconfigured to allow a user to specify other types of patterns notdiscussed above.

Referring back to FIG. 6, a user of the graphical user interface 600 canutilize the console 616 to enter a watchpoint. In the console 616, theuser can create a watchpoint using the HBL language described above, auser can enter a watchpoint that can be applied against the log filesgenerated during an execution of a distributed software program asdescribed above. The replay debugger can then engage in a process(described in detail below) by which a watchpoint is created and the logfiles are scanned to determine if there are any strings within the logfiles that match the patterns specified by the user through the createdwatchpoint.

FIG. 7 illustrates an exemplary watchpoint creation system according toexamples of the disclosure. The system 700 can include one or morewatchpoints 702, which can be generated by a user using adomain-specific language, such as the example of HBL provided above. Inone or more examples, the watchpoints 702 created by one or more usersas described above can be stored in a memory (not pictured). In thisway, the watchpoints can be made more easily available to othercomponents of the system 700 for further processing.

The system 700 can also include a parser 704. In the example of thesystem 700, the parser 704 can be an HBL parser that is specificallyconfigured to work with watchpoints that are declared by a user usingthe HBL language as described above. The parser 704 can parse eachwatchpoint 702 and determine if the watchpoint 702 contains one or moresyntax errors. The parser 704 can also parse each watchpoint 702 todetermine whether or not the watchpoint contains an incompletespecification, an inconsistent specification, or an incorrectspecification. In other words, the parser 704 can parse each and everywatchpoint 702 to determine if the watchpoint contains one or moreerrors that may prevent the system from identifying matching patterns inthe log file.

If the parser 704 determines that such an error exists within one ormore of the watchpoints 702, the parser 704 can generate an errormessage to the user indicating that one or more errors exist in thewatchpoint. Referring back to the example graphical user interfacediscussed with respect to FIG. 6, in one or more examples, the parser704 can generate an error message and transmit the error message toconsole 616 so that the user of the graphical user interface can bealerted that a watchpoint that they specified contains one or moreerrors in how it was specified.

Once the parser 704 has parsed each watchpoint 702 to detect any errorsin how the watchpoint 702 was specified, the watchpoints 702 can beconverted into a regular expression (described above) by a converter706, which can then be applied to the log files. The converter 706 canemploy one or more algorithms that effectively map HBL expressions intoregular expressions. The regular expressions generated by the converter706 can then be applied to the log files (as discussed below).

In parallel to the creation of the watchpoints 702, and their conversionto regular expressions, the log files generated by execution of adistributed software program can be stored and converted into anintermediate format that can be searched by the regular expressions.Thus, the system 700 can include real-time log generator 708 and storedlog generator 710. Real-time log generator 708 can generate log filesduring the real-time execution of a distributed software program asdescribed above. Likewise, stored log generator 710 can also generatelog files based on a prior execution of a distributed software asdescribed above.

Both the real-time log files 708 and the stored log files 710 can beconverted into an intermediate log format (ILF) prior by ILF converter712. Since Regex processing can depend on a standardized representationof log files, the ILF converter 712 can convert the log files providedby elements 708 and 710 into a format that is easier and moreefficiently searched using the regular expressions generated byconverter 706 (i.e., HBL Intermediate Log format). A system may generateHBL ILF format compliant records or logs natively, or alternatively inone more examples the native generated logs can be translated to HBL ILFformatted logs.

The system 700 can also include a watchpoint detector 714. Thewatchpoint detector 714 can take at its inputs the ILFs produced atelement 712 and the regular expressions generated by the converter 706.The watchpoint detector 714 can apply the regular expressions to theILFs and generate detection triggers and matching log records in theILF.

Watchpoint detector 714 can then transmit the matching log records fromthe ILF and the original real-time logs and stored logs generated byelements 708 and 710 to a match detector 716. The match detector 716 canuse the matching log records from the ILF to find the matching logrecords in the real-time and stored logs.

Once the matching log records are found by the match detector 716, theidentified matching logs can be transmitted to a visualization unit 718.Visualization unit 718 can translate the determined matches intovisualizations that can be applied to a graphical user interface (suchas the example provided in FIG. 6). For instance, visualization unit 718can generate the display of the watchpoints in watchpoint interface 618and can apply highlights 620 to the visual progress bar 602.

FIG. 8 illustrates an exemplary method for identifying patterns in aplurality of log files of a replay debugger according to examples of thedisclosure. The method 800 can be implemented in one or more examples bythe system described above with respect to FIG. 7. The method 800 canbegin at step 802, wherein one or more watchpoints are received by auser of a replay debugger. The one or more watchpoints can be specifiedusing a domain-specific language such as HBL, as described above.

After receiving the watchpoints at step 802, the process can move tostep 804, wherein a determination can be made as to whether the one ormore watchpoints received at step 802 are valid. As described above withrespect to FIG. 7, a watchpoint can be analyzed at step 804 to determinewhether the watchpoint contains any syntax errors, incompletespecification, inconsistent specifications, or incorrect specifications.If it is determined at step 804 that watchpoints contain one or moreerrors as described above, the process can move to step 806, wherein theuser is alerted to the error in the watchpoint as described above withrespect to FIG. 7.

If however, the watchpoint is found to not detect any errors at step804, the process can move to step 808, wherein the watchpoint isconverted from the domain-specific language such as HBL into a regularexpression that will be ultimately used to search for matching patternsin the log files.

In parallel to receiving the watchpoints at step 802, the method 800 canalso receive one or more log files at step 814. The log files receivedat step 814 can be generated from the execution of a distributedsoftware program either in real time or at an earlier time as describedabove. Once the log files have been received, the method 800 can move tostep 816, wherein the log files can be converted into an ILF asdescribed above with respect to FIG. 7.

Once the domain specific language specified watchpoints have beenconverted to regular expressions at step 808, and the ILFs have beencreated at step 816, the process can move to step 810, wherein theregular expressions can be applied to the ILFs. In other words, at step810, the regular expressions are used to search for matching patterns inthe ILFs.

After the regular expressions are used to find corresponding matches inthe ILFs at step 810, the process can move to step 812, wherein thematches found in the ILFs are used to determine matches in thecorresponding log files received at step 814, as described above withrespect to FIG. 7. In other words, the matching patterns found in theILFs are then identified within the original log files received at step814. In this way, the patterns in the log files that match theconditions specified by the watchpoints are identified.

After determining the portions of the log files that match the userspecified watchpoints, the replay debugger described above can provide avisualization of where the matches occurred via the graphical userinterface described above with respect to FIG. 6. FIG. 9 illustrates anexemplary method for generating a visualization of a watchpoint within areplay debugger according to examples of the disclosure. The method 900can begin at step 902, wherein the log files that match the specifiedwatchpoints can be received. In one or more examples, the matchesreceived at step 902 can be generated at step 812 as discussed abovewith respect to FIG. 8.

Once the matching log files have been received, the process can move tostep 904, wherein each matching log file can be parsed to extract a timestamp corresponding to the log file. As described above, each log filecan include a time stamp that indicates the chronological time duringthe execution of the distributed software program in which the log filewas generated. Thus, at step 904, each log file that includes a patternthat matches the user-specified watchpoint can be examined to determineat what point in time during execution of the distributed softwareprogram the log file was generated.

Based on the extracted time stamps, the process can move to step 906,wherein a highlight or highlights similar to highlight 620 of FIG. 6 isgenerated on the visual progress bar at a location that correlates withthe chronological time stamp extracted at step 904. In this way, theuser is alerted to the moments in time during the execution of thedistributed software program that the condition that they specifiedusing the watchpoint occurs. Once the visualization has been provided atstep 906, the method 900 can move to step 908, wherein the process isterminated. The conclusion of method 900 thus yields a visual referenceon a graphical user interface that can allow the user to visually seethe moments during an execution of a distributed software program inwhich a specified watchpoint occurs.

FIG. 10 illustrates an example of a computing device in accordance withone embodiment. Device 1000 can be a host computer connected to anetwork. Device 1000 can be a client computer or a server. As shown inFIG. 10, device 1000 can be any suitable type of microprocessor-baseddevice, such as a personal computer, workstation, server, or handheldcomputing device (portable electronic device) such as a phone or tablet.The device can include, for example, one or more of processor 1010,input device 1020, output device 1030, storage 1040, and communicationdevice 1060. Input device 1020 and output device 1030 can generallycorrespond to those described above and can either be connectable orintegrated with the computer.

Input device 1020 can be any suitable device that provides input, suchas a touch screen, keyboard or keypad, mouse, or voice-recognitiondevice. Output device 1030 can be any suitable device that providesoutput, such as a touch screen, haptics device, or speaker.

Storage 1040 can be any suitable device that provides storage, such asan electrical, magnetic, or optical memory, including a RAM, cache, harddrive, or removable storage disk. Communication device 1060 can includeany suitable device capable of transmitting and receiving signals over anetwork, such as a network interface chip or device. The components ofthe computer can be connected in any suitable manner, such as via aphysical bus or wirelessly.

Software 1050, which can be stored in storage 1040 and executed byprocessor 1010, can include, for example, the programming that embodiesthe functionality of the present disclosure (e.g., as embodied in thedevices as described above).

Software 1050 can also be stored and/or transported within anynon-transitory computer-readable storage medium for use by or inconnection with an instruction execution system, apparatus, or device,such as those described above, that can fetch instructions associatedwith the software from the instruction execution system, apparatus, ordevice and execute the instructions. In the context of this disclosure,a computer-readable storage medium can be any medium, such as storage1040, that can contain or store programming for use by or in connectionwith an instruction execution system, apparatus, or device.

Software 1050 can also be propagated within any transport medium for useby or in connection with an instruction execution system, apparatus, ordevice, such as those described above, that can fetch instructionsassociated with the software from the instruction execution system,apparatus, or device and execute the instructions. In the context ofthis disclosure, a transport medium can be any medium that cancommunicate, propagate, or transport programming for use by or inconnection with an instruction execution system, apparatus, or device.The transport readable medium can include, but is not limited to, anelectronic, magnetic, optical, electromagnetic, or infrared wired orwireless propagation medium.

Device 1000 may be connected to a network, which can be any suitabletype of interconnected communication system. The network can implementany suitable communications protocol and can be secured by any suitablesecurity protocol. The network can comprise network links of anysuitable arrangement that can implement the transmission and receptionof network signals, such as wireless network connections, T1 or T3lines, cable networks, DSL, or telephone lines.

Device 1000 can implement any operating system suitable for operating onthe network. Software 1050 can be written in any suitable programminglanguage, such as C, C++, Java, or Python. In various embodiments,application software embodying the functionality of the presentdisclosure can be deployed in different configurations, such as in aclient/server arrangement or through a Web browser as a Web-basedapplication or Web service, for example.

Therefore, according to the above, some examples of the disclosure aredirected to a method comprising: at an electronic device with a displayand an interface configured to accept one or more inputs from a user ofthe electronic device: receiving one or more log files, wherein the oneor more log files are based on a plurality of messages generated by aplurality of components in a distributed computing system during anexecution of a distributed software program implemented on the pluralityof components, and wherein each log file of the one or more log filesincludes a time stamp, and wherein in response to a user providing oneor more watchpoints in a domain-specific language via the interface, theelectronic device is caused to: determine if the one or more userprovided watchpoint declarations include one or more errors, convert theone or more user provided watchpoint declarations into one or moreregular expressions, determine the presence of one or patterns withinthe one or more log files based on the one or more regular expressions,and generate one or more visual indications on the visual progress bar,wherein the one or more visual indications on the visual progress barare based on the one or more log files in which the presence of the oneor more patterns is determined. Additionally or alternatively to one ormore examples disclosed above, the method further comprises: displayinga visual progress bar on the display in a pre-defined area of thedisplay, wherein the visual progress bar includes a first end and asecond end, wherein the first end of the visual progress bar correspondsto the log file with the earliest time stamp of the one or more logfiles, and the second end corresponds to the log file with the latesttimestamp of the one or more log files; and displaying a visualrepresentation in a pre-defined area of the display, wherein the visualrepresentation corresponds to a content of the log file corresponding tothe position of the progress indicator. Additionally or alternatively toone or more examples disclosed above determining the presence of one ormore patterns within the one or more log files based on the one or moreregular expressions includes converting the one or more log files intoone or more intermediate log format files and determining the presenceof the one or more patterns within the one or more intermediate logformat files. Additionally or alternatively to one or more examplesdisclosed above the method further comprises determining acorrespondence between the one or more log files to each intermediatelog file that includes the presence of the one or more patterns.Additionally or alternatively to one or more examples disclosed abovegenerating the one or more visual indications on the visual progress barincludes: determining the value of the time stamp for each of the one ormore log files that corresponds to an intermediate log file thatincludes the presence of the one or more patterns, and generating one ormore markers on the visual progress bar, wherein a position of eachmarker is based on the determined value of the time stamp for each ofthe one or more log files that corresponds to an intermediate log filethat includes the presence of the one or more patterns. Additionally oralternatively to one or more examples disclosed above, the methodfurther comprises: displaying a list in a pre-defined area of thedisplay, wherein the list corresponds to the one or more user providedwatchpoint declarations, wherein each watchpoint of the one or more userprovided watchpoint declarations includes a pre-determined condition,and wherein the list includes the pre-determined conditions.Additionally or alternatively to one or more examples disclosed above helist includes a user interface configured to allow the user to indicatewhether to provide a visual representation of the watchpoints, or toprovide a break point in a replay of the one or more log files when alog file that matches a pre-determined condition is encountered.Additionally or alternatively to one or more examples disclosed abovethe method further comprises: displaying a progress indicator on thevisual progress bar, wherein a position of the progress indicator on thevisual progress bar corresponds to a log file of the one or more logfiles. Additionally or alternatively to one or more examples disclosedabove, the method further comprises: displaying a step forward button ina pre-defined area of the display, wherein the step forward button whenmanipulated by the user causes the position of the progress indicator onthe visual progress bar to move from a first position corresponding to afirst log file to a second position corresponding to a second log file,wherein the time stamp of the second log file is later in time than thetime stamp of the first log file. Additionally or alternatively to oneor more examples disclosed above, the method further comprises:displaying a step back button in a pre-defined area of the display,wherein the step back button when manipulated by the user causes theposition of the progress indicator on the visual progress bar to movefrom a first position corresponding to a first log file to a secondposition corresponding to a second log file, wherein the time stamp ofthe second log file is earlier in time than the time stamp of the firstlog file. Additionally or alternatively to one or more examplesdisclosed above, the method further comprises: displaying a first slideron the visual progress bar, wherein a position of the first slider isconfigured to be manipulated by the user of the graphical userinterface, and wherein the position of the first slider corresponds to afirst log file of the one more log files, displaying a second slider onthe visual progress bar, wherein a position of the second slider isconfigured to be manipulated by the user of the graphical userinterface, and wherein the position of the second slider corresponds toa second log file of the one more log files, wherein in response to thefirst input from the user at the interface, the position of the progressindicator begins at the position of the first slider and moves in adirection from the first end of the visual progress bar to the secondend of the visual progress bar, wherein the log file associated with theprogress indicator changes when the position of the progress indicatorchanges, wherein the visual representation displayed changes when thelog file corresponding to the progress indicator changes, and when theposition of the progress indicator is the same as the position of thesecond slider, the replay is stopped.

Other examples of the disclosure are directed to a computing system, thecomputing system comprising: a display, a user interface caused toreceive inputs from a user of the system, a memory, one or moreprocessors; and one or more programs, wherein the one or more programsare stored in the memory and caused to be executed by the one or moreprocessors, the one or more programs when executed by the one or moreprocessors cause the processor to: receive one or more log files,wherein the one or more log files are based on a plurality of messagesgenerated by a plurality of components in a distributed computing systemduring an execution of a distributed software program implemented on theplurality of components, and wherein each log file of the one or morelog files includes a time stamp, wherein in response to a user providingone or more watchpoints in a domain-specific language via the interface,the processor is further caused to: determine if the one or more userprovided watchpoint declarations include one or more errors, convert theone or more user provided watchpoint declarations into one or moreregular expressions, determine the presence of one or patterns withinthe one or more log files based on the one or more regular expressions,and generate one or more visual indications on the visual progress bar,wherein the one or more visual indications on the visual progress barare based on the one or more log files in which the presence of the oneor more patterns is determined. Additionally or alternatively to one ormore examples disclosed above, the processor is further caused to:display a visual progress bar on the display in a pre-defined area ofthe display, wherein the visual progress bar includes a first end and asecond end, wherein the first end of the visual progress bar correspondsto the log file with the earliest time stamp of the one or more logfiles and the second end corresponds to the log file with the latesttimestamp of the one or more log files, and display a visualrepresentation in a pre-defined area of the display, wherein the visualrepresentation corresponds to a content of the log file corresponding tothe position of the progress indicator. Additionally or alternatively toone or more examples disclosed above, determining the presence of one ormore patterns within the one or more log files based on the one or moreregular expressions includes converting the one or more log files intoone or more intermediate log format files and determining the presenceof the one or more patterns within the one or more intermediate logformat files. Additionally or alternatively to one or more examplesdisclosed above, the processor is further caused to determine acorrespondence between the one or more log files to each intermediatelog file that includes the presence of the one or more patterns.Additionally or alternatively to one or more examples disclosed above,generating the one or more visual indications on the visual progress barincludes: determining the value of the time stamp for each of the one ormore log files that corresponds to an intermediate log file thatincludes the presence of the one or more patterns, and generating one ormore markers on the visual progress bar, wherein a position of eachmarker is based on the determined value of the time stamp for each ofthe one or more log files that corresponds to an intermediate log filethat includes the presence of the one or more patterns. Additionally oralternatively to one or more examples disclosed above, the processor isfurther caused to: display a list in a predefined area of the display,wherein the list corresponds to the one or more user provided watchpointdeclarations, wherein each watchpoint of the one or more user providedwatchpoint declarations includes a pre-determined condition, and whereinthe list includes the pre-determined conditions. Additionally oralternatively to one or more examples disclosed above, the list includesa user interface caused to allow the user to indicate whether to providea visual representation of the watchpoints, or to provide a break pointin a replay of the one or more log files when a log file that matches apre-determined condition is encountered. Additionally or alternativelyto one or more examples disclosed above, the processor is further causedto: display a progress indicator on the visual progress bar, wherein aposition of the progress indicator on the visual progress barcorresponds to a log file of the one or more log files. Additionally oralternatively to one or more examples disclosed above, the processor isfurther caused to: display a step forward button in a pre-defined areaof the display, wherein the step forward button when manipulated by theuser causes the position of the progress indicator on the visualprogress bar to move from a first position corresponding to a first logfile to a second position corresponding to a second log file, whereinthe time stamp of the second log file is later in time than the timestamp of the first log file. Additionally or alternatively to one ormore examples disclosed above, the processor is further caused to:display a step back button in a pre-defined area of the display, whereinthe step back button when manipulated by the user causes the position ofthe progress indicator on the visual progress bar to move from a firstposition corresponding to a first log file to a second positioncorresponding to a second log file, wherein the time stamp of the secondlog file is earlier in time than the time stamp of the first log file.Additionally or alternatively to one or more examples disclosed above,the processor is further caused to: display a first slider on the visualprogress bar, wherein a position of the first slider is caused to bemanipulated by the user of the graphical user interface, and wherein theposition of the first slider corresponds to a first log file of the onemore log files, display a second slider on the visual progress bar,wherein a position of the second slider is caused to be manipulated bythe user of the graphical user interface, and wherein the position ofthe second slider corresponds to a second log file of the one more logfiles, wherein in response to the first input from the user at theinterface, the position of the progress indicator begins at the positionof the first slider and moves in a direction from the first end of thevisual progress bar to the second end of the visual progress bar,wherein the log file associated with the progress indicator changes whenthe position of the progress indicator changes, wherein the visualrepresentation displayed changes when the log file corresponding to theprogress indicator changes, and when the position of the progressindicator is the same as the position of the second slider, the replayis stopped.

Other examples of the disclosure are directed to a computer readablestorage medium storing one or more programs, the one or more programscomprising instructions, which, when executed by an electronic devicewith a display and a user input interface, cause the device to: receiveone or more log files, wherein the one or more log files are based on aplurality of messages generated by a plurality of components in adistributed computing system during an execution of a distributedsoftware program implemented on the plurality of components, and whereineach log file of the one or more log files includes a time stamp,display a visual progress bar on the display in a pre-defined area ofthe display, wherein the visual progress bar includes a first end and asecond end, wherein the first end of the visual progress bar correspondsto the log file with the earliest time stamp of the one or more logfiles and the second end corresponds to the log file with the latesttimestamp of the one or more log files, and wherein in response to auser providing one or more watchpoints in a domain-specific language viathe interface, the electronic device is caused to: determine if the oneor more user provided watchpoint declarations include one or moreerrors, convert the one or more user provided watchpoint declarationsinto one or more regular expressions, determine the presence of one orpatterns within the one or more log files based on the one or moreregular expressions, and generate one or more visual indications on thevisual progress bar, wherein the one or more visual indications on thevisual progress bar are based on the one or more long files in which thepresence of the one or more patterns is determined. Additionally oralternatively to one or more examples disclosed above, the device isfurther caused to: display a progress indicator on the visual progressbar, wherein a position of the progress indicator on the visual progressbar corresponds to a log file of the one or more log files, and displaya visual representation in a pre-defined area of the display, whereinthe visual representation corresponds to a content of the log filecorresponding to the position of the progress indicator. Additionally oralternatively to one or more examples disclosed above, the device isfurther caused to: display a play button in a pre-defined area of thedisplay, wherein the first and second inputs from the user includeclicking on the displayed play button determining the presence of one ormore patterns within the one or more log files based on the one or moreregular expressions includes converting the one or more log files intoone or more intermediate log format files and determining the presenceof the one or more patterns within the one or more intermediate logformat files. Additionally or alternatively to one or more examplesdisclosed above, the device is further caused to determine acorrespondence between the one or more log files to each intermediatelog file that includes the presence of the one or more patterns.Additionally or alternatively to one or more examples disclosed above,generating the one or more visual indications on the visual progress barincludes: determining the value of the time stamp for each of the one ormore log files that corresponds to an intermediate log file thatincludes the presence of the one or more patterns, and generating one ormore markers on the visual progress bar, wherein a position of eachmarker is based on the determined value of the time stamp for each ofthe one or more log files that corresponds to an intermediate log filethat includes the presence of the one or more patterns, display a listin a pre-defined area of the display, wherein each log file of the oneor more log files include one or more variables, and wherein the listincludes a listing of the one or more variables included in the log filecorresponding to the position of the progress indicator. Additionally oralternatively to one or more examples disclosed above, the device isfurther caused to: display a list in a pre-defined area of the display,wherein the list corresponds to the one or more user provided watchpointdeclarations, wherein each watchpoint of the one or more user providedwatchpoint declarations includes a pre-determined condition, and whereinthe list includes the pre-determined conditions. Additionally oralternatively to one or more examples disclosed above, the list includesa user interface configured to allow the user to indicate whether toprovide a visual representation of the watchpoints, or to provide abreak point in a replay of the one or more log files when a log filethat matches a pre-determined condition is encountered. Additionally oralternatively to one or more examples disclosed above, the device isfurther caused to: display a progress indicator on the visual progressbar, wherein a position of the progress indicator on the visual progressbar corresponds to a log file of the one or more log files. Additionallyor alternatively to one or more examples disclosed above, the device isfurther caused to: display a step forward button in a pre-defined areaof the display, wherein the step forward button when manipulated by theuser causes the position of the progress indicator on the visualprogress bar to move from a first position corresponding to a first logfile to a second position corresponding to a second log file, whereinthe time stamp of the second log file is later in time than the timestamp of the first log file. Additionally or alternatively to one ormore examples disclosed above, the device is further caused to: displaya step back button in a pre-defined area of the display, wherein thestep back button when manipulated by the user causes the position of theprogress indicator on the visual progress bar to move from a firstposition corresponding to a first log file to a second positioncorresponding to a second log file, wherein the time stamp of the secondlog file is earlier in time than the time stamp of the first log file.Additionally or alternatively to one or more examples disclosed above,the device is further caused to: display a first slider on the visualprogress bar, wherein a position of the first slider is configured to bemanipulated by the user of the graphical user interface, and wherein theposition of the first slider corresponds to a first log file of the onemore log files, display a second slider on the visual progress bar,wherein a position of the second slider is configured to be manipulatedby the user of the graphical user interface, and wherein the position ofthe second slider corresponds to a second log file of the one more logfiles, wherein in response to the first input from the user at theinterface, the position of the progress indicator begins at the positionof the first slider and moves in a direction from the first end of thevisual progress bar to the second end of the visual progress bar,wherein the log file associated with the progress indicator changes whenthe position of the progress indicator changes, wherein the visualrepresentation displayed changes when the log file corresponding to theprogress indicator changes, and when the position of the progressindicator is the same as the position of the second slider, the replayis stopped.

The foregoing description, for purpose of explanation, has beendescribed with reference to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit the disclosure to the precise forms disclosed. Many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described in order to best explain theprinciples of the techniques and their practical applications. Othersskilled in the art are thereby enabled to best utilize the techniquesand various embodiments with various modifications as are suited to theparticular use contemplated.

Although the disclosure and examples have been fully described withreference to the accompanying figures, it is to be noted that variouschanges and modifications will become apparent to those skilled in theart. Such changes and modifications are to be understood as beingincluded within the scope of the disclosure and examples as defined bythe claims.

This application discloses several numerical ranges in the text andfigures. The numerical ranges disclosed inherently support any range orvalue within the disclosed numerical ranges, including the endpoints,even though a precise range limitation is not stated verbatim in thespecification, because this disclosure can be practiced throughout thedisclosed numerical ranges.

The above description is presented to enable a person skilled in the artto make and use the disclosure, and it is provided in the context of aparticular application and its requirements. Various modifications tothe preferred embodiments will be readily apparent to those skilled inthe art, and the generic principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the disclosure. Thus, this disclosure is not intended to belimited to the embodiments shown but is to be accorded the widest scopeconsistent with the principles and features disclosed herein. Finally,the entire disclosure of the patents and publications referred in thisapplication are hereby incorporated herein by reference.

What is claimed is:
 1. A method, comprising: at an electronic devicewith a display and an interface configured to accept one or more inputsfrom a user of the electronic device: receiving one or more log files,wherein the one or more log files are based on a plurality of messagesgenerated by a plurality of components in a distributed computing systemduring an execution of a distributed software program implemented on theplurality of components, and wherein each log file of the one or morelog files includes a time stamp; and wherein in response to a userproviding one or more watchpoints in a domain-specific language via theinterface, the electronic device is caused to: determine if the one ormore user provided watchpoint declarations include one or more errors;convert the one or more user provided watchpoint declarations into oneor more regular expressions; determine the presence of one or patternswithin the one or more log files based on the one or more regularexpressions; and generate one or more visual indications on the visualprogress bar, wherein the one or more visual indications on the visualprogress bar are based on the one or more log files in which thepresence of the one or more patterns is determined.
 2. The method ofclaim 1, wherein the method comprises: displaying a visual progress baron the display in a pre-defined area of the display, wherein the visualprogress bar includes a first end and a second end, wherein the firstend of the visual progress bar corresponds to the log file with theearliest time stamp of the one or more log files, and the second endcorresponds to the log file with the latest timestamp of the one or morelog files; and displaying a visual representation in a pre-defined areaof the display, wherein the visual representation corresponds to acontent of the log file corresponding to the position of the progressindicator.
 3. The method of claim 1, wherein determining the presence ofone or more patterns within the one or more log files based on the oneor more regular expressions includes converting the one or more logfiles into one or more intermediate log format files and determining thepresence of the one or more patterns within the one or more intermediatelog format files.
 4. The method of claim 3, wherein the method furthercomprises determining a correspondence between the one or more log filesto each intermediate log file that includes the presence of the one ormore patterns.
 5. The method of claim 4, wherein generating the one ormore visual indications on the visual progress bar includes: determiningthe value of the time stamp for each of the one or more log files thatcorresponds to an intermediate log file that includes the presence ofthe one or more patterns; and generating one or more markers on thevisual progress bar, wherein a position of each marker is based on thedetermined value of the time stamp for each of the one or more log filesthat corresponds to an intermediate log file that includes the presenceof the one or more patterns.
 6. The method of claim 1, the methodfurther comprising: displaying a list in a pre-defined area of thedisplay, wherein the list corresponds to the one or more user providedwatchpoint declarations, wherein each watchpoint of the one or more userprovided watchpoint declarations includes a pre-determined condition,and wherein the list includes the pre-determined conditions.
 7. Themethod of claim 6, wherein the list includes a user interface configuredto allow the user to indicate whether to provide a visual representationof the watchpoints, or to provide a break point in a replay of the oneor more log files when a log file that matches a pre-determinedcondition is encountered.
 8. The method of claim 2, the method furthercomprising displaying a progress indicator on the visual progress bar,wherein a position of the progress indicator on the visual progress barcorresponds to a log file of the one or more log files.
 9. The method ofclaim 2, the method further comprising: displaying a step forward buttonin a pre-defined area of the display, wherein the step forward buttonwhen manipulated by the user causes the position of the progressindicator on the visual progress bar to move from a first positioncorresponding to a first log file to a second position corresponding toa second log file, wherein the time stamp of the second log file islater in time than the time stamp of the first log file.
 10. The methodof claim 2, the method further comprising: displaying a step back buttonin a pre-defined area of the display, wherein the step back button whenmanipulated by the user causes the position of the progress indicator onthe visual progress bar to move from a first position corresponding to afirst log file to a second position corresponding to a second log file,wherein the time stamp of the second log file is earlier in time thanthe time stamp of the first log file.
 11. The method of claim 2, themethod further comprising: displaying a first slider on the visualprogress bar, wherein a position of the first slider is configured to bemanipulated by the user of the graphical user interface, and wherein theposition of the first slider corresponds to a first log file of the onemore log files; displaying a second slider on the visual progress bar,wherein a position of the second slider is configured to be manipulatedby the user of the graphical user interface, and wherein the position ofthe second slider corresponds to a second log file of the one more logfiles; wherein in response to the first input from the user at theinterface, the position of the progress indicator begins at the positionof the first slider and moves in a direction from the first end of thevisual progress bar to the second end of the visual progress bar,wherein the log file associated with the progress indicator changes whenthe position of the progress indicator changes, wherein the visualrepresentation displayed changes when the log file corresponding to theprogress indicator changes, and when the position of the progressindicator is the same as the position of the second slider, the replayis stopped.
 12. A computing system, comprising: a display; a userinterface configured to receive inputs from a user of the system; amemory; one or more processors; and one or more programs, wherein theone or more programs are stored in the memory and configured to beexecuted by the one or more processors, the one or more programs whenexecuted by the one or more processors cause the processor to: receiveone or more log files, wherein the one or more log files are based on aplurality of messages generated by a plurality of components in adistributed computing system during an execution of a distributedsoftware program implemented on the plurality of components, and whereineach log file of the one or more log files includes a time stamp;wherein in response to a user providing one or more watchpoints in adomain-specific language via the interface, the processor is furthercaused to: determine if the one or more user provided watchpointdeclarations include one or more errors; convert the one or more userprovided watchpoint declarations into one or more regular expressions;determine the presence of one or patterns within the one or more logfiles based on the one or more regular expressions; and generate one ormore visual indications on the visual progress bar, wherein the one ormore visual indications on the visual progress bar are based on the oneor more log files in which the presence of the one or more patterns isdetermined.
 13. The computing system of claim 12, wherein the process isfurther caused to: display a visual progress bar on the display in apre-defined area of the display, wherein the visual progress barincludes a first end and a second end, wherein the first end of thevisual progress bar corresponds to the log file with the earliest timestamp of the one or more log files and the second end corresponds to thelog file with the latest timestamp of the one or more log files; anddisplay a visual representation in a pre-defined area of the display,wherein the visual representation corresponds to a content of the logfile corresponding to the position of the progress indicator.
 14. Thesystem, of claim 12, wherein determining the presence of one or morepatterns within the one or more log files based on the one or moreregular expressions includes converting the one or more log files intoone or more intermediate log format files and determining the presenceof the one or more patterns within the one or more intermediate logformat files.
 15. The system of claim 14, wherein the processor isfurther caused to determine a correspondence between the one or more logfiles to each intermediate log file that includes the presence of theone or more patterns.
 16. The system of claim 15, wherein generating theone or more visual indications on the visual progress bar includes:determining the value of the time stamp for each of the one or more logfiles that corresponds to an intermediate log file that includes thepresence of the one or more patterns; and generating one or more markerson the visual progress bar, wherein a position of each marker is basedon the determined value of the time stamp for each of the one or morelog files that corresponds to an intermediate log file that includes thepresence of the one or more patterns.
 17. The system of claim 12,wherein the processor is further caused to: display a list in apredefined area of the display, wherein the list corresponds to the oneor more user provided watchpoint declarations, wherein each watchpointof the one or more user provided watchpoint declarations includes apre-determined condition, and wherein the list includes thepre-determined conditions.
 18. The system of claim 12, wherein the listincludes a user interface configured to allow the user to indicatewhether to provide a visual representation of the watchpoints, or toprovide a break point in a replay of the one or more log files when alog file that matches a pre-determined condition is encountered.
 19. Thesystem of claim 13, wherein the processor is further caused to display aprogress indicator on the visual progress bar, wherein a position of theprogress indicator on the visual progress bar corresponds to a log fileof the one or more log files.
 20. The system of claim 13, wherein theprocessor is further caused to: display a step forward button in apre-defined area of the display, wherein the step forward button whenmanipulated by the user causes the position of the progress indicator onthe visual progress bar to move from a first position corresponding to afirst log file to a second position corresponding to a second log file,wherein the time stamp of the second log file is later in time than thetime stamp of the first log file.
 21. The system of claim 13, whereinthe processor is further caused to: display a step back button in apre-defined area of the display, wherein the step back button whenmanipulated by the user causes the position of the progress indicator onthe visual progress bar to move from a first position corresponding to afirst log file to a second position corresponding to a second log file,wherein the time stamp of the second log file is earlier in time thanthe time stamp of the first log file.
 22. The system of claim 13,wherein the processor is further caused to: display a first slider onthe visual progress bar, wherein a position of the first slider isconfigured to be manipulated by the user of the graphical userinterface, and wherein the position of the first slider corresponds to afirst log file of the one more log files; display a second slider on thevisual progress bar, wherein a position of the second slider isconfigured to be manipulated by the user of the graphical userinterface, and wherein the position of the second slider corresponds toa second log file of the one more log files; wherein in response to thefirst input from the user at the interface, the position of the progressindicator begins at the position of the first slider and moves in adirection from the first end of the visual progress bar to the secondend of the visual progress bar, wherein the log file associated with theprogress indicator changes when the position of the progress indicatorchanges, wherein the visual representation displayed changes when thelog file corresponding to the progress indicator changes, and when theposition of the progress indicator is the same as the position of thesecond slider, the replay is stopped.
 23. A non-transitory computerreadable storage medium storing one or more programs, the one or moreprograms comprising instructions, which, when executed by an electronicdevice with a display and a user input interface, cause the device to:receive one or more log files, wherein the one or more log files arebased on a plurality of messages generated by a plurality of componentsin a distributed computing system during an execution of a distributedsoftware program implemented on the plurality of components, and whereineach log file of the one or more log files includes a time stamp;display a visual progress bar on the display in a pre-defined area ofthe display, wherein the visual progress bar includes a first end and asecond end, wherein the first end of the visual progress bar correspondsto the log file with the earliest time stamp of the one or more logfiles and the second end corresponds to the log file with the latesttimestamp of the one or more log files; and wherein in response to auser providing one or more watchpoints in a domain-specific language viathe interface, the electronic device is caused to: determine if the oneor more user provided watchpoint declarations include one or moreerrors; convert the one or more user provided watchpoint declarationsinto one or more regular expressions; determine the presence of one orpatterns within the one or more log files based on the one or moreregular expressions; and generate one or more visual indications on thevisual progress bar, wherein the one or more visual indications on thevisual progress bar are based on the one or more long files in which thepresence of the one or more patterns is determined.
 24. The computerreadable storage medium of claim 23, wherein the device is furthercaused to: display a progress indicator on the visual progress bar,wherein a position of the progress indicator on the visual progress barcorresponds to a log file of the one or more log files; and display avisual representation in a pre-defined area of the display, wherein thevisual representation corresponds to a content of the log filecorresponding to the position of the progress indicator.
 25. Thecomputer readable storage medium of claim 23, wherein the device isfurther caused to: display a play button in a pre-defined area of thedisplay, wherein the first and second inputs from the user includeclicking on the displayed play button determining the presence of one ormore patterns within the one or more log files based on the one or moreregular expressions includes converting the one or more log files intoone or more intermediate log format files and determining the presenceof the one or more patterns within the one or more intermediate logformat files.
 26. The computer readable storage medium of claim 25,wherein the device is further caused to determine a correspondencebetween the one or more log files to each intermediate log file thatincludes the presence of the one or more patterns.
 27. The computerreadable storage medium of claim 26, wherein generating the one or morevisual indications on the visual progress bar includes: determining thevalue of the time stamp for each of the one or more log files thatcorresponds to an intermediate log file that includes the presence ofthe one or more patterns; and generating one or more markers on thevisual progress bar, wherein a position of each marker is based on thedetermined value of the time stamp for each of the one or more log filesthat corresponds to an intermediate log file that includes the presenceof the one or more patterns; display a list in a pre-defined area of thedisplay, wherein each log file of the one or more log files include oneor more variables, and wherein the list includes a listing of the one ormore variables included in the log file corresponding to the position ofthe progress indicator.
 28. The computer readable storage medium ofclaim 23, wherein the device is further caused to: display a list in apre-defined area of the display, wherein the list corresponds to the oneor more user provided watchpoint declarations, wherein each watchpointof the one or more user provided watchpoint declarations includes apre-determined condition, and wherein the list includes thepre-determined conditions.
 29. The computer readable storage medium ofclaim 28, wherein the list includes a user interface configured to allowthe user to indicate whether to provide a visual representation of thewatchpoints, or to provide a break point in a replay of the one or morelog files when a log file that matches a pre-determined condition isencountered.
 30. The computer readable storage medium of claim 24,wherein the device is further caused to display a progress indicator onthe visual progress bar, wherein a position of the progress indicator onthe visual progress bar corresponds to a log file of the one or more logfiles.
 31. The computer readable storage medium of claim 24, wherein thedevice is further caused to: display a step forward button in apre-defined area of the display, wherein the step forward button whenmanipulated by the user causes the position of the progress indicator onthe visual progress bar to move from a first position corresponding to afirst log file to a second position corresponding to a second log file,wherein the time stamp of the second log file is later in time than thetime stamp of the first log file.
 32. The computer readable storagemedium of claim 24, wherein the device is further caused to: display astep back button in a pre-defined area of the display, wherein the stepback button when manipulated by the user causes the position of theprogress indicator on the visual progress bar to move from a firstposition corresponding to a first log file to a second positioncorresponding to a second log file, wherein the time stamp of the secondlog file is earlier in time than the time stamp of the first log file.33. The computer readable storage medium of claim 24, wherein the deviceis further caused to: display a first slider on the visual progress bar,wherein a position of the first slider is configured to be manipulatedby the user of the graphical user interface, and wherein the position ofthe first slider corresponds to a first log file of the one more logfiles; display a second slider on the visual progress bar, wherein aposition of the second slider is configured to be manipulated by theuser of the graphical user interface, and wherein the position of thesecond slider corresponds to a second log file of the one more logfiles; wherein in response to the first input from the user at theinterface, the position of the progress indicator begins at the positionof the first slider and moves in a direction from the first end of thevisual progress bar to the second end of the visual progress bar,wherein the log file associated with the progress indicator changes whenthe position of the progress indicator changes, wherein the visualrepresentation displayed changes when the log file corresponding to theprogress indicator changes, and when the position of the progressindicator is the same as the position of the second slider, the replayis stopped.